In the manufacture of many different products, there is a need to attach multiple layers of same or different materials to one another. This can be carried out by forming holes by drilling or machining through multiple layers of material and inserting an elongate fixing means, such as a rivet, a screw or a bolt into the hole.
In certain circumstances, the depth of the remaining holes or the thickness of the materials is either not critical, or the depth or thickness is known to a sufficient degree from the design drawings and known factors from the manufacture of the components being drilled and fixed. In these instances, a bolt or rivet can be chosen based upon design parameters known from the design and component specification process.
However, in other applications, the thickness of the materials being fixed may not be known, this can be due to manufacturing tolerances resulting from the manufacturing process used to make the materials to be fastened together. Further, in certain applications, it is of importance to accurately match the length of the fixing means to the depth of the hole very precisely. This is a particular problem in high precision and safety critical products such as aircraft components and assemblies. The problem can particularly arise where multiple layers of differing materials are used, particularly where composites are used, whose depth can vary depending upon the particular lay-up of the fibres in composite components.
It is therefore necessary in some situations to accurately measure hole depth before choosing an appropriately dimensioned fixing means for fixing the multiple components together.
The present invention therefore seeks to address these issues and to provide an improved manufacturing and assembly process.